Europium-doped yttrium oxide is widely used in fluorescent lamps as a red-emitting phosphor. Typically, this phosphor is produced in its simplest form, e.g., Type 2345 manufactured by the Chemical & Metallurgical Division of GTE Products Corporation, Towanda, Pa., by firing a commercially obtained mixture of coprecipitated the yttrium (III) oxide and europium (III), and then milling and sieving the fired material to produce the finished phosphor powder. This phosphor powder typically comprises tiny crystallites which have been agglomerated into particles having an average size of 3 to 3.5 by Coulter Counter.
A second form of this phosphor, e.g., Type 2342 manufactured by the Chemical & Metallurgical Division of GTE Products Corporation, Towanda, Pa., is formulated by blending small amounts of chemical fluxing agents, i.e., Li.sub.2 CO.sub.3, K.sub.2 CO.sub.3, and H.sub.3 BO.sub.3, with a commercially obtained coprecipitated mixture of yttrium-europium oxide. When this blend is fired, the Li.sub.2 CO.sub.3, K.sub.2 CO.sub.3, and H.sub.3 BO.sub.3 fluxes enhance the growth of the particles and favor more of a single-crystal morphology for the resultant powder. This powder is also finished by milling and sieving so that its average size is 4.0 to 4.5 by Coulter Counter.